1. Field of the Invention
The present invention relates to a method for a semiconductor device fabrication. More particularly, the present invention relates to a method for processing a poly defect.
2. Description of the Related Art
In semiconductor manufacturing process, polysilicon is widely used to form a conductive layer, especially a gate conductive layer. However, defects are often formed on a polysilicon layer, called poly defects, while forming the polysilicon layer. The poly defects usually affect the subsequent photolithography and etching process, so that the device yield is decreased because of the poly defects. The defects are mostly formed by impurities left in a chamber used for forming the polysilicon layer. Most of the impurities are polysilicon particles left by the process for forming the polysilicon layer. When the reaction temperature is high or the concentration of the silicon source gas is high, the polysilicon particles are easily formed and adsorbed on the wall of the chamber. When too many polysilicon particles have been adsorbed, the polysilicon particles fall on chips and pollute them. The problem of impurities is avoided by cleaning the chamber, but the cleaning process takes one and a half to two days. Therefore, the throughput of devices is decreased when the reaction chamber is idle.
Conventionally, the poly defects are removed by a scrubber or a sprayer. However, the scrubber or sprayer generates stress, so that a recess or vacancy is generated and the oxide layer formed in the previous process is exposed. This recess or vacancy causes leakage current and open circuit or short circuit generation to result in the failure of the whole chip.
FIGS. 1A through 1B are schematic, cross-sectional views showing the conventional processing steps for removing a poly defect. Referring to FIG. 1A, a substrate 10 is provided, and an oxide layer 12 including a gate oxide layer and a field oxide layer is formed on the substrate 10. A polysilicon layer 14 is formed on the oxide layer 12. A poly defect 16 is formed on the polysilicon layer 14 surface simultaneous with the formation of the polysilicon layer 14. The height of the poly defect 16 is about 0.5-3 micrometer.
Referring to FIG. 1B, the poly defect 16 is removed by scrubber or sprayer. The scrubber or sprayer generates stress, so that a recess or vacancy 18 is generated and the oxide layer 12 formed in the previous process is exposed. Therefore, the poly defect 16 causes a leakage current and an open circuit or a short circuit which result in the failure of the whole chip. The effect of removing the poly defect 16 by scrubber or sprayer is limited.